Narrow light aperture and method of making the same



Feb. 15 1927. 1,618,117

J. T. TSCHQPP NARROW LIGHT APERTURE AND METHOD OF MAKING THE SAME Filed July 6, 1926 Inventor: Jacob T lisdaqqo, 25 V b His Attorney.

larger scale; and Fig. 3

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.or through the film and the mama 1 .1.. 15.1921.

UNITED .sm-gsp;trim OFFICE.

JACOB '1. TSGHOPP, 0F SCHENECTLDY, NEW YORK ASBIGNOE TO GENERAL ELECTRIC COIPANY, A CORPORATIQH OF NEW YORK. i

v numow mem unmunn hm) 'mnrnon or name ran SAME.

Application filed July 6, 1926. Serial No. 120,590.

My invention is applicable to apparatus which sound is recorded on and reproduced from a film, as for example, a moving picture film, but is useful also for other purposes. More particularl my invention relates to that part of suc apparatus by means of which a light beam of the desired width en ages the film in the process of making t e record or passes through the film in the process of reproducing sounds recorded thereon. An ob ect of my invention is the provision of improved means useful in such apparatus for determining the aperture through'which lightmay pass to process of makin the same.

y invention will be better understood from the following description taken in connection with the accompanying drawing, and its scope will be pointed out in the appended claims. I

Referring to the drawing, Fig. 1 1s a diagrammatic view showing apparatus 1nvolving my invention; 2 is a detail of the apparatus shown in i 1 drawn to a s ows' a further detail drawn to a still er scale; and Fig. 4 shows a modification.

In Fi 1 I have shown an arrangement by whie the sounds previously recorded on 'a film may be converted into electrical 1mpulses which correspond in wave form to the sound waves and which if suitably amlified and fed into a tele hone receiver or lbud speaker will repro uce the ori nal sounds. The film 1 is illustrated as o the type commonly employed for .motion pictures but having a sound record 2 thereon of a form such as shown for example in the copending a plication of Charles A. Home, Serial No. 4 1,229 which is assigned to the same assignee as the present application. The'film 1 is shown passing over a supporting and guiding pulley or roller 3 which is carried by the shaft 4. That portion 5 of the pulley through which light must pass is of transparent material. Within the pulley I have shown the photoelectric cell 6. Outside is the source of light 9 shown as an electric lam having a ribbon filament'lO, and arrange in alignment between the source and the window (not shown) of the photoelectric cell are the lens 11 and aperture holder 12 whereby light rays from the source are focused on the aperture and in passing therethrough enter the photo-electric cell. In the complete apparatus additional means may be found desirable to shield the photoelectric cell from the light of the source 9 and from other sources.

\ The holder 12, which for convenience I have illustrated as formed of two similar parts, supports the prism 13 therebetween through w ich light from the lamp 9 passes to thefilm. The rism 13 .may be constructed of any suitable transparent substance, as for example, glass or uartz but due to its more desirable optica ualities I refer to use quartz for this mem er.

. n Fig. 3 I have shown the prism enlarged many times over its actual size'in order better to illustrate its construction. Its two side faces 14 and 15 are parallel with each other and its side face 16 is at right angles thereto. 0 posite the face 16, two inclined faces 17 an 18 are ground on it, giving the prism a wedge-shaped edge portion 19. Care is taken to have these inclined faces ground flat and to have them form a sharp edge where they meet. This edge is then carefully ground off and polished so as to produce a flat face 20 havin a width corresponding to the desired wi th of the light beam reaching the film. Some of the best results have been obtained with a beam width of about one mil. The opposite .face 16 is also ground fiat and polished. To limit the light beam to that emerging. from the aperture formed by narrow face 20, the faces 17 and 18 and also faces 14 and 15 if desired, although this may not be necessary, are covered with some opaque substance. I prefer to polish these surfaces and silver them whereby the light and heat rays are reflected away rather than absorbed.

The holder 12 is adjustably mounted by suitable means (not shown) very close to the surface of the moving film and the quartz prism 13 is set back in the holder just enough to insure its always being out of actual contact with the film.

In using the apparatus shown in Fig. 1, it willof course be understood that the lens, shown only diagrammatically in Fig. 1, is of such a character and is so placed that light from the source 9 is thrown in a bright band of suitable dimensions on the prism 13. If instead of reproducing the record carried by the film, a new film is to be exposed in themakin of a new record, the

ceptwhere it passes in front of the narrow aperture plovided by the prism. Variations in the amount of, light reaching the film through the a rture in accordance with the 4 ing recorded mayhe pro duced in a variety of ways. One we or pro-- ducing such variations is disclose in the aforementioned application of Charles A. Hoxie by which method a record is produced. having the appearance of that shown in Fl .1;

l f desired the prism l3 may have a curved rear face, as shown, for example, in the modified form illustrated by Fig. a. p In this fig are the prism 22 is shown having a convex rear face 23which may be suitably curved to cause the-light raysengaging it to convergeor focus'at the narrow face 24 corresound waves sponding to the face 0f the form shown in Fig.3. In this modification I have also shown the as sector-she e in cross sectionhaving side faces 25 an 26. With this form of prism it may be found desirable to cover with an opaque covering only those portions of the side faces which are near the narrow face 24 or it may be omitted entirely particularly if the holder extends fully to the narrow face.

What I claim as new and desire to secure by Letters latent of the United States, is 1. Themethodof making a narrow light aperture by means of a transparent memher which comprises forming an edge at one side of the member, and cutting away the- .edge to form a narrow face; of the'width' tion and a narrow hat of the aperture desired. 1 v

2. The method of making anarrow liglgt aperture by means of a transparent mem r which 5 comprises forming an edge at one side or the member, cuttin away the ed e to form a narrow face'of t e width of the aperture desired and covering the surface ofithe member to cause the light traversing it to be limited to a beam of the width. 01'

the narrow face. 1 p

3. The method'of making a narrow light aperture by means of a transparent member which comprises bevelin the sides of the member to form a sidcs."

transvers y of t I -shaped edge, grinding off the edge to form a plane narrow face ha f ancient-r 4.11m comhination,-means for guiding a moving film, and means for admitting a narrovv beam of ligght thereto comprising a transparent mem er having a wedgeshaoiped portion arranged adjacent the-fihn an terminating in a narrow face.

In combination, means torguiding a moving "film, means for admitting a narrow beam of li ht thereto comprising a transparent man er having a wedge-shaped portion arranged adjacent the film andterminating in a narrow face, and means for obstructing the passage of light through the side faces of the wedge-shaped portion.

6., In combination, a roller adapted to support a moving film and means for admitting a=narrowheam or light to the film comprising a prism of transparent material the portion of the prism adjacent the film wedge-shaped and terminatingin a narrow plane face and an opaque covering for the sides of the wedgeshape portion.

- 7. lln combination, a roller having a transparent portion ada ted to support and guide a moving" film, a p etc-electric device within the roller, 21. source of light, and means arranged between the source and the film for permitting a narrow beam only to pass through the film to the device, comprising a prism of transparent material having a wedge-she. ed edge e film'andterminating'in a narrow face, a holder for the prism engaging opposite sides thereof and an o aque cggering on'the sides of the wedge-s aped e e atransparent prism havin a air of in clined faces forming a w face connecting said arranged adjacent to and s. aperture forming device comprising 7 10. An aperture forming device com risinga. guartz prism havin a air 0 m clined aces formi a w geaped portion and a narrow at face connecting said inclined faces, and a silver coating on said inclined faces. I

In witness whereof I have hereto set my hand this 2nd day 0 July, 1926.

Y 5 Jason T. 'rscnorn 

